Avivo HD Vs Purevideo HD

Nvidias Dynamic Contrast Enhancement and Colour Enhancement

With the 9600 and 9800 series of graphics cards Nvidia have added two new video features to PureVideo HD. Dynamic Contrast Enhancement takes each frame and calculates enhancement values for that frame which is a change from older methods of contrast enhancement which apply the same changes to every scene, regardless of whether enhancement is required.Â Â Colour Enhancement analyses the tone of an image and dynamically adjusts it for each frame. The example Nvidia use to describe this is “skin tones changing from flat to vibrant”.

We decided to test these options and the results follow, it should be noted that we also enabled the noise reduction feature in the Nvidia drivers and set it to a level similar to ATI. (ATI enable noise reduction by default). In theory, this should represent the best image quality Nvidia has to offer, without changing edge enhancement values. When we asked ATI what settings we should use for testing, ‘default’ was the response, so we can assume that the screenshots produced so far represent their best image quality.

Please note for these tests we have supplied lossless quality BMP’s so you are able to look at the high resolution images yourself. That said, we are aware that not everyone will be on high speed broadband so there are JPEG versions available as well (by simply clicking the images), however please be aware that JPEG format is a lossy format, and introduces its own artifacting via compression. They are merely included as an fast loading reference for your perusal – the BMPS should be viewed for closer study.

Image 6: Planet Earth, Fresh Water 25m 16s

Media Enthusiast Observations:
Our final image test has a few surprises on the Nvidia card. Firstly with all the blue, which caused issues in previous scenes, it could have been possible for the image to be ruined again. This does not happen and the water actually becomes deeper in colour. There is also a distant fish on the top left of the image which is more visible on Nvidia now than it is on ATI. There is however one stand out problem with the Nvidia capture which surprised us. The dark fish near the front left of the image actually loses further detail in the new Nvidia image, a complete contrast to the improvements we saw in detail levels for previous comparisons.

Analysis Overview
Original NV Left / Enhanced Right

Colour improvements

Expert Observations:
If we firstly study the blue fish front left, we can see it looks considerably more vivid than before. Subjecting the fish to analysis we notice that the magenta content on the enhanced image has been reduced by 10-15%, the cyan content has not been touched. The removal of magenta from the blue has enhanced the colour and it gives the fish more vibrancy. Analysing the ocean in the background shows the enhanced mode has reduced the yellow content by around 10-15% which again enhances the primarly colours of cyan and magenta which combine to make a rich blue. Again Stuart’s observations with the dark coloured fish in the foreground would verify the fact that the enhanced algorithm is trying to boost contrast by adding 3-4% extra black into dark zones. While this isn’t really needed overall this image is better with the enhanced settings.